Q and A: 2007 Final and Proposed Regulations for n-Propyl Bromide (nPB)

Through its Significant New Alternatives Policy (SNAP)
Program, the U.S. Environmental Protection Agency (EPA)
is allowing or proposing to allow the use of n-propyl
bromide (nPB) as an alternative to ozone-depleting
substances (ODS) in some, but not all, end uses. The SNAP
program implements section 612 of the Clean Air Act,
which requires EPA to evaluate substitutes for ODSs to
ensure they minimize risk to human health and the
environment. This fact sheet answers commonly asked
questions about EPA’s regulations on the
appropriate use of nPB as a substitute for CFC-113,
HCFC-141b, and methyl chloroform.

What is EPA deciding about how nPB may be
used? EPA is finding nPB acceptable for use as a
substitute for CFC-113 and methyl chloroform in metals,
electronics, and precision cleaning in a final decision.
EPA is also issuing a separate proposal for other uses of
nPB.

* Data from a number of facilities and from
modeling indicate likely exposures in excess of
potentially protective levels, and therefore,
unacceptable health risks for users of nPB-based
adhesives and aerosols.

Am I allowed to use nPB now that EPA has issued a
proposed rule? Yes, you may continue to use nPB until EPA
finalizes this proposed rule. Be sure to note information
below about potentially protective exposure levels and
ways to avoid overexposure, listed below.

What is nPB? How do I know if I am working with
nPB? Also called 1-bromopropane, nPB is a nonflammable
organic solvent with a strong odor. Its Chemical
Abstracts Service Registry Number (CASRN) is 106-94-5.
nPB‘s main uses are in degreasing and spray
adhesives. Brand name products containing nPB include
Abzol, Ensolv and Solvon cleaners, Ensolv-NDI aerosol
cleaner, Whisper Spray, and fire retardant Soft Seam
adhesives, among others. The manufacturer‘s
Material Safety Data Sheet (MSDS) contains information on
the formulation and whether it contains nPB.

What exposure levels does EPA consider
potentially protective?

EPA is considering the following ranges of exposures
on an eight-hour time-weighted basis to be potentially
protective of human health:

17 to 22 parts per million (ppm), to protect the
female reproductive system

18 to 30 ppm, to protect the male reproductive
system

20 ppm, to ensure reproductive success.

How did EPA decide what exposure levels for nPB
are potentially protective? EPA reviewed all available toxicological and
occupational case studies as well as manufacturers‘
recommended guidelines and third party assessments. The
Agency coordinated its review with key federal agencies
including the Occupational Safety and Health
Administration (OSHA) and the National Institutes for
Occupational Safety and Health (NIOSH). The
Agency‘s risk assessment underwent independent
expert peer review.

What are the health effects of overexposure to
nPB? The following effects have been reported among
workers with high exposures to nPB:

Leg weakness and pain leading to a difficulty with
standing and walking (stumbling)

Numbness, tingling, and prickling in legs

Headache, dizziness, nausea, memory and
concentration difficulties

Studies on animals indicate a range of effects on
the liver, nervous system, and the male and female
reproductive systems.

How can I prevent overexposure to nPB? If you are working with nPB:

Move away from the source of nPB when you are not
directly using it.

Use personal protective equipment, such as flexible
laminate gloves, aprons, and goggles.

If you are using nPB in solvent cleaning equipment,
avoid drafts over the equipment, remove parts no faster
than 10 feet per minute, and tilt parts so that solvent
will drain out instead of collecting on the parts.

Until the proposed rule is finalized, if you use
nPB in aerosols or adhesives, install and use local
exhaust ventilation designed to attain a face velocity
of 100 to 150 feet per minute.

Companies using nPB should take advantage of the
manufacturers' exposure monitoring programs or set up an
exposure monitoring program of their own. Or, consider
switching to a less toxic alternative.

How do EPA‘s acceptable exposure levels
compare to industry standards and regulatory
requirements?In December 2004, the American Conference of
Governmental Industrial Hygienists (ACGIH) established a
Threshold Limit Value (TLV) of 10 ppm for nPB as an
8-hour time-weighted average of exposure. If EPA were to
rely on this TLV of 10 ppm, the Agency would likely
propose the same acceptability decisions described here.
To date, OSHA has not issued a Permissible Exposure
Limit (PEL) for nPB. At OSHA‘s request, the
National Toxicology Program will perform a number of
studies on the effects of nPB. When these studies are
completed (studies could take several years), OSHA could
set a mandatory nPB workplace exposure limit that would
supersede EPA‘s recommended exposure level.

What are the environmental impacts of
nPB?At the latitude of the US, nPB has an ozone
depletion potential (ODP) of 0.013 to 0.018. At tropical
latitudes, nPB has an ODP of 0.071 to 0.100, close to
that of methyl chloroform and HCFC-141b. EPA is basing
its proposed decision on the ODP in the US. nPB may
contribute to smog and is regulated as a volatile organic
compound.
Although nPB is not currently regulated as a
hazardous waste, EPA recommends that you dispose of it as
any other halogenated solvents to avoid impacts on
aquatic life (The LC50, the concentration at which 50% of
test animals die, is 67 mg/L for fathead minnows). nPB
has a low tendency to concentrate in living organisms
with a bioconcentration factor of 23. It is moderately
mobile in soil with a Koc value of 330. nPB tends to
volatilize and breaks down easily in water, with a
hydrolysis half-life of 26 days.

Why is EPA changing from its earlier proposal for
adhesives and aerosols?Since EPA‘s initial proposal in 2003,
additional exposure data and studies on the adverse
effects of nPB on human health have become available
which are listed in the proposed regulation.

When will EPA issue a final ruling on nPB for
adhesives and aerosols?EPA plans on issuing a final rule in 2008. The
actual date will depend on the number and complexity of
the issues the public raises in response to the proposed
rule.

How can I get more information about
nPB?

ContactMargaret Sheppard;
Tel: (202) 343-9163Review EPA Docket EPA maintains information on nPB
in a public docket. You can access the docket by: